Method for heating and cooling food products

ABSTRACT

A method and device for heating and cooling, such as for the sterilization, pasteurization, drying and/or roasting, of food products, such as nuts and beans, for example whole and crushed peanuts and coffee and cocoa beans, comprising bringing the raw food products into contact with a heated granular material, separating of the granular material from the food products after the heat transfer from the heated granular material to the food products, and the subsequent cooling of the food products, the cooling of the food products taking place by means of a granular material which is first conveyed to the product to be cooled and is separated therefrom after the cooling.

The invention relates to a method for heating and cooling, such as forthe sterilization, pasteurization, drying and/or roasting, of foodproducts, such as nuts and beans, for example whole and crushed peanutsand coffee and cocoa beans, comprising bringing the raw food productsinto contact with a heated granular material, separating the granularmaterial from the food products after the heat transfer from the heatedgranular material to the food products, and the subsequent cooling ofthe food products.

Such a method is disclosed in British Patent Specification 1,530,784.This discloses the roasting of coffee beans, comprising the bringing ofthe green beans into contact with a solid, heated material, which is nota fluid, which is inert under operating conditions and which gives upits heat optimally to the green beans, the subsequent separation of theheat-transferring material and the beans, and the final cooling of theroasted coffee beans. Said cooling takes place by spraying the stillhot, roasted coffee beans with water and by blowing air over the beans,as a result of which the husks can also be removed. The granularmaterial which has been separated from the coffee beans is reused aftereach separation and conveyed to a new charge of green coffee beans.

In the roasting process described, gases are released, such as watervapour, hydrocarbons and inorganic compounds, which escape from thesystem as process emissions. This escape means an inherent energy lossand the release of odours and pollutants into the environment.

In addition, in the process described, the product quality is adverselyaffected by the supply of water and air for cooling the roasted product.In practice, it is found that such a cooling process cannot be regulatedwith sufficient accuracy, in particular as regards the regulation of themoisture content of the product at the end of the process. As a resultof which a sufficiently homogeneous cooling cannot be achieved and an aleast unsatisfactorily reproducible product quality is achieved.

In addition, the cooling of the still hot, roasted product with waterand air means inherent energy loss because the heat extracted with thewater and the air escape from the system.

In practice, large quantities of air appear to be necessary for coolingaccording to this known process. All this air has to be taken in, fedthrough and discharged, which requires suitable installations for thepurpose which demand an appreciable quantity of energy for theiroperation.

A certain amount of water is always present in the system which is usedfor the known method. This water brings about corrosion of thecomponents in said system.

The object of the invention is to provide a method and a device forheating and cooling food products, such as peanuts and coffee and cocoabeans, which method and device experience the abovementioneddisadvantages to a lesser extent.

This object is achieved, according to the present invention, in that thefood products are cooled by means of a granular material which is firstconveyed to the product to be cooled and is separated therefrom afterthe cooling. The employment of a granular material makes the coolingprocess simple to carry out as a closed system, so that energy loss andthe escape of gases can be considerably reduced. In addition, nospraying of water has to be used, which avoids an uneven coolingoccurring and/or water being absorbed by the product to be cooled orcooled product, which effects generally have a disadvantageous influenceon the produce quality. In addition, the occurrence of corrosion isprevented in that no water is supplied and as little condensation aspossible occurs. The granular material has properties and a chemicalcomposition which are such that it does not react chemically in thecooling process with the product to be cooled, it easily absorbs heatfrom the product to be cooled and does not give up any water to theproduct to be cooled. Preferably, the granular material is a porousmaterial, so that it can contain, for example, water as coolant.

Preferably, the granular material is reused for cooling the foodproducts. Consequently, a closed system is possible, as a result ofwhich process emissions can be treated further--in order to removeundesirable substances or to burn them and prevent the occurrence ofundesirable odours--before escaping into the ambient air, and energyloss can be minimized. Some material saving can also be achieved by thereuse of the granular material.

According to the present invention it is not necessary for the roastingprocess and the cooling process to be strictly separated as regards theflows of granular material. According to the present invention, agranular material can be provided which is eminently suitable for theroasting and the cooling of nuts and beans. The partial separation ofthe granular material which is used for the roasting of the foodproducts from the then roasted food products is sufficient, it beingpossible to use the unseparated granular material in the cooling of theroasted food products.

The method according to the present invention results in energy savingin relation to the roasting process and the cooling process comparedwith the energy consumption of known methods and, in particular,compared with that method which does not include or includes a partialwaste-gas treatment. In addition, the invention provides thermalpost-incineration of the process emissions. The amount of exhaust gasesto be emitted in total is still only 2% to 12% compared with the knownmethods. The low amounts of granular material compared with the amountsof product results, as regards the equipment, in a more compact design,or a smaller external size, of the roasting process means, depending onthe choice of granular material and depending on the free space neededfor mixing product and granular material. Less energy will then beabsorbed by the means of the system itself, which means a reduction inenergy loss. A small thermal post-incinerator is sufficient. Althoughthe method according to the invention does result in more systemcomponents than the performance of the known methods, the lines are ofmuch more limited extent.

According to another aspect of the invention, the granular materialwhich has served to cool the roasted food products and has consequentlybeen heated is conveyed to the granular material which has served toroast the raw food products and has consequently been cooled.Consequently, the heat which the granular material has absorbed in thecooling process can be given up to the granular material which has beencooled in the roasting process. This reduces the energy loss which wouldoccur as a result of allowing the cooling of the granular materialheated up in the cooling process and the heating up of the granularmaterial cooled in the roasting process to occur separately from oneanother.

The process emissions may contain various chemical substances for whichit is undesirable that they are discharged into the ambient air. It ispossible to convert the undesirable substances into other substanceswhich are not undesirable or less undesirable by incineration orpost-incineration of said process emissions. It is therefore possible toprevent evil-smelling odours escaping into the environment of theproduction facility, which odours are produced, in particular, in theroasting and cooling of nuts and beans. The post-incineration can takeplace using post-incineration means known for the purpose.

By processing the process emissions in this way, it is possible, inaddition, to convey the post-incinerated process emissions to thegranular material which has been separated for reuse from the roastedfood products and brought back to the beginning of the roasting processto give up its heat essentially to the granular material before escapingfrom the device. This achieves an appreciable energy saving.

Preferably, the process emissions from various process stages areconveyed to a common system of post-incineration means. This results ina limitation of the means needed and makes efficient insulationpossible, so that an optimum energy saving is achieved.

The present invention also relates to the device for the carrying out ofthe method according to the invention.

Said device contains a section in which the roasting process takes placeand/or a section in which the cooling process takes place and a sectionin which the post-incineration process takes place. The inventionprovides means with which emissions originating from the roastingprocess and/or the cooling process are post-incinerated.

In connection with the reuse of the granular material which is used inthe roasting process, the section in which the roasting process takesplace comprises means for roasting the raw food products and means forregenerating the granular material. Insofar as it is undesirable thatthe granular material remains mixed with the roasted food products, thesection in which the roasting process takes place comprises means forseparating the granular material from the food products.

In connection with the reuse of the granular material which is used inthe cooling process, the section in which the cooling process takesplace comprises means for cooling the roasted food products and meansfor regenerating the granular material. In this connection, the meansfor cooling the roasted food products may contain means for mixing thegranular material and the roasted food products.

Insofar as it is undesirable that granular material remains mixed withthe cooled food products, the section in which the cooling process takesplace comprises means for separating the granular material from thecooled food products. In this connection, said separating means may bedivided into means for a rough degree of separation and means for a finedegree of separation in order to improve the result of the separation.

The means for separating the granular material from the roasted orcooled food products may also be omitted. The separation then takesplace integrally with the roasting process or the cooling process,respectively.

According to a further aspect of the invention, the section in which thepost-incineration process takes place comprises means for thepost-incineration of the emissions which are conveyed from at least oneof the sections in which the roasting process or the cooling process,respectively, takes place. The process emissions can be post-incineratedfrom one or more of their sources to a greater or lesser degree.

The present invention also relates to the granular material which can beused in connection with or in the method and device according to theinvention.

Preferably, the granular material is capable of absorbing heat from, orgiving it up to, its environment in a reversible process. As a result,reuse of granular material can be achieved, which is advantageous formaterial saving. In addition, it is then possible to use the samegranular material both in the roasting process and in the coolingprocess. For this purpose, it is unnecessary for the flows of granularmaterial in both processes to be in communication with one another. Asregards costs and interchangeability, it is, in particular, moreefficient to use one type of granular material for both processes whichare connected with one another than to use a separate type of granularmaterial for each process.

Preferably, the granular material is a porous material. The granularmaterial is then capable of absorbing, for example, water as coolantwithout the risk occurring of water being transferred to the cooled nutsand beans, which would adversely affect the product quality.

Various known substances can be taken as granular material. It appearsthat material which contains silicon and aluminium oxides is eminentlysuitable. The granular material may also contain metals, such as steelgranules, and/or plastics.

Preferably, a microporous silicon oxide (XSi_(n) O_(m), where Xcomprises one or more metals, for example Al, Bo, Mn, Ti), such asaluminium silicon oxide, aluminium phosphate which is incorporated inthe oxide lattice, or zeolites with, for example, Bo or Ti incorporatedare taken as granular material. These materials are mainly used ascatalysts in synthesis processes and as microsieves for selectiveremoval of certain molecules from, for example, mixtures ofhydrocarbons.

The aluminium silicon oxides are characterized by a Si/Al ratio of 1 toinfinity. The ends of this scale are formed by zeolite A (gismondine)with a Si/Al ratio of 1 and silica zeolites with a Si/Al ratio of (much)greater than 1. In the IUPAC mnemonic coding, the following, forexample, belong to the class of the aluminium silicon oxides: LTA (Lindetype A), Na₁₂ [Al₁₂ Si₁₂ O₄₈ ].27H₂ O, isotype SAPO-42; LTL (Linde typeL), K₆ Na₃ [Al₉ Si₂₇ O₇₂ ].21H₂ O, FAU (faujasite), Na₅₈ [Al₅₈ Si₁₃₄O₃₄₈ ].24H₂ O, isotype SAPO-37; FER (ferrierite), Na₂ Mg₂ [Al₆ Si₃₀ O₇₂].18H₂ O, isotypes ZSM-5, NU-23: 5≦Si/Al<25; MOR (mordenite), Na₈ [Al₈Si₄₀ O₉₆ ].24H₂ O; and MFI (ZSM-5), Na_(n) [Si_(96-n) Al_(n) O₁₉₂ ].16H₂O (n≦8), isotypes silicalite-1, boralite, TS-1, (Si, Ge)-MFI. In theIUPAC mnemonic coding, the following, for example, belong to the classof the aluminium phosphates which are incorporated in the oxide lattice(alpos): AFI (AlPO₄ -5), [Al₁₂ P₁₂ O₄₈ ].(C₃ H₇)₄ NOH.xH₂ O, isotypesSAPO-5, SSZ-24.

Modified zeolites can also be used as granular material. In thisconnection, the modification relates to the provision on or in thezeolite, for the purpose of improving the separating properties, of ametal core, a metal external shell or a mixture with metal powder, inparticular, in such a way that the composition of metal and zeoliteacquires ferromagnetic properties. As a result, the typical propertiesof the zeolites are retained, while separating procedures which make useof magnets can be used to remove the zeolites from the products.

As described above, metals can also be used as granular material. Inthis connection, ferromagnetic and ferrimagnetic materials arepreferably used. The advantage of this is that separating procedureswhich make use of magnets can then be used to remove the granularmaterial from the products. Examples of such ferromagnetic materials aresteel alloys, nickel alloys (alnico) and ferroxdur (BaO-6Fe₂ O₃).Examples of ferrimagnetic materials are ferrites (XFe₂ O₄, in which X isa metal, such as, for example, Cu, Mg, Ni, Fe or Zn, trade nameFerroxcube), garnets (3X₂ O₃ -5Fe₂ O₄, where X is a rare earth, such as,for example, Pr, Nd, Pm, Sa, Eu, Gd, Tb, Dy or Y, trade nameFerroxplana), silicon/iron compounds and nickel/iron compounds(Permalloy).

As described above, plastics can also be used as granular material. Inthis connection, a heat-resistant type of plastic, such as, for example,PVDF and PP (polypropylene), is preferably used. The advantage of thisis that a high wear resistance and high chemical resistance areobtained. Examples of such plastics are teflon and plastics with"enclosed" electrostatic charges, as a result of which said plasticshave advantageous properties in relation to the separation of thegranular material and the products.

Preferably, silica zeolite is taken as granular material. The zeolitesare heat-resistant, chemically inert, non-toxic and are used, interalia, as fillers in animal feed.

Preferably, zeolite A, with which the best results are obtainedaccording to tests carried out, is taken as granular material. Zeolite Acontains Na₁₂ [Al₁₂ Si₁₂ O₄₈ ].27H₂ O. This material provides thefollowing advantages for the roasting process. An appreciable amount ofheat is released during the adsorption of water vapour which escapesfrom the product to be roasted during the roasting process, whichintensifies the roasting process. As a porous material, it has a poresize which is such that only water can be adsorbed, as a result of whichthe granular material does not become "contaminated" by large-moleculecompounds, as a result of which the granular material would not be, orwould scarcely be, suitable for reuse. As a result of the wateradsorption the hydrocarbons are released into an atmosphere which is lowin water vapour, which is energetically favourable for the thermalpost-incineration of these vapours. As a consequence of the release ofthe heat of adsorption, less than half of the mass of granular materialotherwise needed is sufficient to cause the process to proceed withinthe boundary conditions set.

Zeolite A provides the following advantages for the cooling process.Like silica zeolite, zeolite A can absorb an appreciable amount ofwater, as a result of which the heat capacity proves to be two to threetimes as high as that of the dry granular material. As a result, asmaller mass of granular material is sufficient to carry out the coolingprocess within the conditions set for the purpose.

Because very small amounts of exhaust gas, compared with the currentamounts of exhaust gas, are released both from the roasting process andfrom the cooling process as a result of the use of a zeolite, the vapourprocessing can be carried out by thermal post-incineration using arelatively small structural unit.

The steel spheres, silica zeolite and zeolite A mentioned as granularmaterials have mutually different properties. Unlike the steel granules,the zeolites have a porous structure, as a result of which they canadsorb water. Zeolite A can only adsorb water, during which process ahigh heat of adsorption is released, while silica zeolite can adsorb, inaddition to a much larger amount of water than zeolite A, also all sortsof other substances because of its different pore sizes, in whichprocess virtually no heat of adsorption is released. The differences inproperties result in different performances. The choice of material forthe granular material is therefore dependent on the various performancesdesired. An overview of the characterizing properties of the threematerials mentioned is given in Table 1 and of the advantages anddisadvantages in Table 2.

In the case of the method and device according to the invention, thestarting point in each case is spherical granules having a diameter ofbetween approximately 2 and 5 mm. It is not out of the question that theuse of granules having larger or smaller diameters or granules having ashape other than spherical yield good or better results.

On the basis of the process conditions as regards temperatures, moisturecontents and roasting and cooling speeds needed for a particulardesirable product quality, the heat transfer between the three types ofgranular material mentioned and the nuts and beans to be roasted or tobe cooled has been investigated. In this connection, model calculationshave been carried out for an ideal situation with parameters such as theheat-transferring surface, the dwell time of the granular material inthe process and the coefficients of heat transfer. The result of thecalculations relates to the mass of granular material compared with themass of the product, which ratio is necessary to meet the boundaryconditions set. The mass ratios found are given in Table 3 for theroasting process and in Table 4 for the cooling process.

The possibility that granular material gets stuck in grooves or cavitiesin the products, referred to as inclusion, has been investigated bycarrying out tests. In said tests, it has been found that coffee andcocoa beans and peanuts are sensitive to high mixing forces, with theresult that product damage occurs and the risk of inclusion increases.In the case of coffee beans, a small degree of inclusion of the zeolitegranules having a diameter of 3 mm has been observed. In the case ofthose granules having a diameter of 2.2 mm, no inclusion has beenobserved. The effect on the occurrence of inclusion in the case ofgranule diameters greater than 3 mm could not be investigated becausesaid granules were not available. It is expected, however, thatinclusion can be prevented by a good choice of granule size. In thisconnection, surface smoothness, particle mass, stickiness and the degreeof product damage play a part.

To heat the granular material, it is advantageous if said material ispolar because it can then also be heated in a simple way by means of agenerally known microwave oven. In addition, the heating can then beaccurately regulated in a simple way, which benefits the product controland, consequently, the product quality.

To separate the granular material from the roasted or cooled product, itis advantageous if said granular material has magnetic properties sothat the separation can take place in a simple way by means of permanentmagnets or electromagnets.

Several separating procedures have been investigated. Complete removalof the steel balls from the products can be achieved by means ofmagnetic separation. The product losses observed during the tests with asomersault magnet can be reduced to a fairly far-reaching extent byoptimizing the procedure, a different way of separating with magnets andby various subsequent treatment steps. For zeolite granules, thevibrating screen gives a removal result of 99.99% in the case of coffeebeans, 99.0% in the case of cocoa beans and 99.94% in the case ofpeanuts. The product loss in the case of coffee beans and peanuts isless than 0.1%. In the case of cocoa beans, various subsequent screeningsteps are necessary to limit the product loss because their particlesize is situated in a wide range around the screen size employed incarrying out the tests and the granule size is variable. The speed ofseparation is dependent on the number of separating steps to be taken.This speed can be of the order of magnitude of seconds in the case ofseparation with magnets and the use of vibrating screens.

The invention will be illustrated in greater detail below by referenceto the accompanying drawing, in which some exemplary embodiments areelaborated.

FIG. 1 shows, in diagrammatic form, the device according to theinvention in one embodiment.

FIG. 2 shows, in diagrammatic form, the device according to theinvention in another embodiment.

As is evident from FIG. 1, the device according to the inventioncomprises a section 1 in which the roasting process takes place, asection 2 in which the cooling process takes place and a section 3 inwhich the post-incineration process takes place.

The section 1, in which the roasting process takes place, comprisesmeans 4 for roasting the raw food products, which means 4 may alsooptionally comprise means (not shown) for mixing the granular materialand the food products, means 5 for separating the granular material fromthe food products and means 6 for regenerating the granular material.

In addition, said section 1 comprises lines 7 for conveying raw foodproducts to the means 4 for roasting of said raw food products, lines 8for conveying the roasted food products plus the granular material tothe means 5 for separating said granular material and the roasted foodproducts, lines 9 for discharging the roasted food products to thesection 2 in which the cooling process takes place, lines 10 fordischarging emissions to section 3, in which the post-incinerationprocess takes place, lines 11 for conveying the granular materialseparated from the roasted food products to the means 6 for regeneratingthe granular material, lines 12 for conveying the regenerated granularmaterial to the means 4 for roasting the raw food products fed in, lines13 for conveying the emissions post-incinerated in section 3 to themeans 6 for regenerating the granular material, lines 14 for removingthe emissions post-incinerated in the section 3, which have previouslybeen conveyed to the means 6 for regenerating the granular material, andlines 13 for conveying the emissions produced in the means 6 to means 29for the post-incineration of said emissions. If desired, granularmaterial can be let in or out of the section 1 via lines 15. Line 16indicates that, for example, natural gas or electricity can be fed in,for example, for an incineration process or a microwave oven,respectively.

The section 2, in which the cooling process takes place, comprises means17 for cooling the roasted food products, which means 17 may alsooptionally comprise means (not shown) for mixing the granular materialand the roasted food products, means 18 for separating to a rough degreethe granular material from the cooled food products, means 19 forseparating to a fine degree the granular material from the cooled foodproducts and means 20 for regenerating the granular material.

In addition, said section 2 comprises lines 9 for conveying the roastedfood products to the means 17 for cooling said roasted food products,lines 21 for conveying the cooled food products plus the granularmaterial to the means 18 for separating to a rough degree said granularmaterial and the cooled food products, lines 22 for conveying the cooledfood products plus the granular material to the means 19 for separatingto a fine degree said granular material from the cooled food products,lines 23 for removing the finished food products for further processingoutside the device according to the invention, lines 24 for dischargingemissions to the section 3 in which the post-incineration process takesplace, lines 25 for conveying the granular material separated from thecooled food products to the means 20 for regenerating the granularmaterial and lines 26 for conveying the regenerated granular material tothe means 17 for cooling the roasted food products fed in. If desired,granular material can be let in or out of the section 2 via lines 27.The lines 28 indicate that, for example, cooling water can be fed to themeans 20 and removed from the latter for cooling the granular material.

The roasting and cooling of the raw or roasted food products,respectively may take place in batches or in a continuous flow. Themeans 4 and 17 for roasting or cooling, respectively, the food productsmay comprise, for example, a column containing a stirring mechanism or adrum. The means 5, 18 and 19 for separating the granular material fromthe food products may comprise, for example, vibrating screens orseparating means based on permanent magnets or electromagnets or forelectrostatic separation. All this is dependent on the type of granularmaterial used.

The section 3 in which the post-incineration process takes placecomprises means 29 for post-incinerating the emissions which are fed infrom the sections 1 and 2 in which the roasting process or the coolingprocess, respectively, takes place. In addition, said section 3comprises lines 10 for feeding in emissions from the section 1 in whichthe roasting process takes place, lines 24 for conveying emissions fromthe section 2 in which the cooling process takes place, lines 13 fordischarging the post-incinerated emissions to the section 1 in which theroasting process takes place and lines 32 for discharging thepost-incinerated emissions from the system. The line 30 indicates that,for example, natural gas can be fed to means 29 for thepost-incineration process.

FIG. 2 shows an embodiment of the device according to the inventionother than the one in FIG. 1. In the device according to FIG. 2, noseparation of the granular material from the roasted food products takesplace in the section 1, in which the roasting process takes place. Inaddition, FIG. 2 shows the situation in which means 19 are provided oncefor the separation of the granular material from the food products, inwhich no lines are present for conveying the emissions produced in means6 to the means 29 for the post-incineration of said emissions, and inwhich no lines are present for discharging post-incinerated emissionsfrom the system. A simpler device according to the invention is obtainedwith the embodiment according to FIG. 2.

The device according to FIG. 2 comprises lines 31 for conveying thegranular material separated from the cooled food products to the means 6in the section 1 for regenerating the granular material, after which itis used in the roasting process.

                                      TABLE 1                                     __________________________________________________________________________    Molecular sieves         Metal                                                Zeolite type A                                                                            Silica       Steel grinding balls                                 __________________________________________________________________________    Na Si Al oxide (Si/Al = 1)                                                                Si Al oxide (Si >> Al)                                                                     Carbon steel                                         Water adsorption only                                                                     Adsorption of water and                                                                    No adsorption                                                    other substances                                                  Maximum water adsorption                                                                  Moximum water adsorption 1                                                                 Not applicable                                       210 g/kg    kg/kg                                                             H.sub.ads = 4200 kJ/kg H.sub.2 O                                                          H.sub.ads = 0 kJ/kg                                                                        Not applicable                                       C.sub.p dry = 0.7 kJ/kgK                                                                  C.sub.p dry = 0.7 kJ/kgK                                                                   C.sub.p = 0.5 kJ/kgK                                 C.sub.p = wet = 1.4 kJ/kgK                                                                C.sub.p wet = 2.4 kJ/kgK                                          Bulk density '2 580 kg/m.sup.3                                                            Bulk density = 430 kg/m.sup.3                                                              Bulk density = 4990 kg/m.sup.3                       C.sub.p dry = 406 kJ/m.sup.3 K                                                            C.sub.p dry = 301 kJ/m.sup.3 K                                                             C.sub.p = 2495 kJ/m.sup.3 K                          C.sub.p wet = 812 kJ/m.sup.3 K                                                            C.sub.p wet = 1032 kJ/m.sup.3 K                                   __________________________________________________________________________     Dimensions: spheres 2-5 mm                                               

                                      TABLE 2                                     __________________________________________________________________________    Advantages and                                                                disadvantages per                                                             system  Zeolite                                                               component                                                                             A         Silica    Steel                                             __________________________________________________________________________    Advantages                                                                    Roasting                                                                              Lowest mass compar-                                                           ed with product mass                                                          Control by HF                                                                           Control by HF                                                                           Control by                                                possible  possible  induction possible                                                            100% removal from                                 Cooling Retains water up to                                                                     Lowest mass compar-                                                                     the product                                               high temperature                                                                        ed with product mass                                        Separation                  No minimum                                        Regeneration                                                                          Only water by                                                                           No minimum                                                                              temperature for                                           adsorption, no                                                                          temperature for                                                                         desorption                                                contaminated exhaust                                                                    desorption                                                          gas on desorption                                                                                 Wear resistance                                   Various Relatively cheap    good                                                      zeolite                                                               Disadvantages                                                                 Roasting                    No stable mixture                                                             as a result of too                                                            high a mass                                                                   compared with                                                                 product mass                                      Cooling                     No stable mixture                                                             as a result of too                                                            high a mass                                                                   compared with                                                                 product mass                                      Separation                                                                            No guarantee of 100%                                                                    No guarantee of 100%                                                removal from product                                                                    removal from product                                        Regeneration                                                                          Desorption                                                                    temperature of >                                                              260° C. necessary                                              Various Wear due to fracture                                                                    Wear due to fracture                                                                    Corrosion possible                                __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________         T of           stirred bed of                                                 incoming                                                                           stirred container,                                                                      product, granular material                                Product                                                                            granular                                                                           batch     continuous                                                of   material                                                                           Zeolite A                                                                          Zeolite A                                                                          Zeolite A                                                                          Zeolite A                                            (°C.)                                                                       (°C.)                                                                       No Q ads.                                                                          Q ads.                                                                             No Q ads.                                                                          Q ads.                                                                             Silica                                                                           Steel                                        __________________________________________________________________________    Coffee                                                                        20-220                                                                             400  5.0  2.5  3.1  1.9  3.1                                                                              5.8                                               300  11.2 3.0  5.3  2.5  5.3                                                                              10.1                                         Cocoa                                                                         85-135                                                                             250            3.0  0.6  3.2                                                                              5.0                                          Peanuts                                                                       20-85                                                                              250            1.6  --   1.6                                                                              2.8                                               180            2.4  0.45 2.5                                                                              4.6                                          __________________________________________________________________________     Calculation results of mass ratio for granular material and product           Zeolite A2 = 2.36 m                                                           Silica 2.2 m                                                                  Steel 2.2 mm                                                             

                  TABLE 4                                                         ______________________________________                                                              stirred bed of product, granular                                   T incoming material continuous                                     Product dT (°C.)                                                                  granules (°C.)                                                                    Zeolite A  Silica                                                                             Steel                                   ______________________________________                                        Coffee                                                                        220-30     15         3.4        2.2  10.1                                    100-30     15         2.2        1.3  6.5                                     Cocoa                                                                         135-70     15         1.3        0.7  3.8                                     Peanuts                                                                       85-30      15         2.7        1.8  9.0                                     ______________________________________                                         Calculation results of mass ratio for granular material and product           Zeolite A2 = 2.36 mm                                                          Silica 2.2 mm                                                                 Steel 2.2 mm                                                             

We claim:
 1. Method of heating and cooling raw food productscomprising:a) heating a raw food product by contacting the food productwith heated, non-food, granular material; b) cooling the heated foodproduct; and c) separating the food product from the granularmaterialwherein the heating or cooling of the food product during stepa), or step b) respectively, is effected by contacting the food productwith a heat transfer material comprising porous granular zeolite, thegranular zeolite being at a different temperature from the temperatureof the food product.
 2. A method according to claim 1 wherein the heatedgranules comprise the granular zeolite, the different temperature beinga higher temperature.
 3. A method according to claim 1 wherein step b)is effected by contacting the heated food product with cooled granularmaterial.
 4. A method according to claim 3 wherein the cooled granulescomprise the granular zeolite.
 5. A method according to claim 1 whereinheating step a) is conducted to sterilize, pasteurize, dry or roast thefood product.
 6. A method according to claim 5 wherein the food productcomprises nuts, beans, whole peanuts, crushed peanuts, coffee beans orcocoa beans.
 7. A method according to claim 1 wherein the zeolitecomprises zeolite A.
 8. A method according to claim 1 wherein thezeolite comprises aluminum phosphate incorporated in the zeolitelattice.
 9. A method according to claim 1 wherein the granular materialcomprises zeolite and has magnetic properties to facilitate separationof the granular material from the food product.
 10. A method accordingto claim 9 wherein the ferromagnetic granular zeolite material compriseszeolite granules having a metal core, a metal external shell or a metalpowder component, the metal being ferromagnetic or ferrimagnetic toprovide the ferromagnetic properties.
 11. A method according to claim 1wherein the granular material comprises a polar material and is suitablefor heating in a microwave oven.
 12. A method according to claim 1wherein the granular material is reused for cooling the food products.13. A method according to claim 1 wherein the granular material ispartially separated from the heated food product, and the separatedgranular material is subsequently used in cooling the heated foodproduct in step b).
 14. A method according to claim 13 wherein granularmaterial heated from use in cooling step b) is conveyed to granularmaterial cooled from use in heating step a).
 15. A method according toclaim 1 wherein heating step a) generates process emission vapors and atleast some of the process emission vapors are collected and thermallyprocessed by a post-incineration unit.
 16. A method according to claim15 wherein the granular material is recycled from step c) to step a) andheat generated by the post-incineration unit is transferred to thegranular material separated in step c).
 17. A method according to claim15 wherein process emissions from multiple process stages are conveyedto a common post-incineration unit.
 18. A method of sterilizing,pasteurizing, drying or roasting a food product selected from the groupconsisting of nuts, beans, whole peanuts, crushed peanuts, coffee beansand cocoa beans the method comprising:a) heating a food product bycontacting the food product with warmer granular material; b) coolingthe heated food product by contacting the food product with coolergranular material; and c) separating the granular material from thecooled food product;wherein the granular material in both steps a) andb) comprises a zeolite having a pore size such that water vapour isadsorbed in preference to large-molecule compounds and wherein thezeolite releases heat upon adsorption of water vapour.
 19. A methodaccording to claim 18 wherein the zeolite comprises spherical granulesof zeolite A having a particle size of from approximately 2 toapproximately 5 mm.
 20. Method of heating and cooling raw food productsthat release water vapor on heating, the method comprising:a) heatingthe raw food product by contacting the food product with heated,non-food, granular material; b) cooling the heated food product; and c)separating the food product from the granular materialwherein theheating or cooling of the food product during step a), or step b)respectively, is effected by contacting the food product with a granularheat transfer material having a pore size such as to preferentiallyadsorb water vapor wherein the granular heat transfer material releasesheat during the adsorption of water vapour.
 21. A method according toclaim 1 wherein the granular material comprises a material selected fromthe group consisting of plastic, polytetrafluoroethylene andpolypropylene.